Here are some examples of words that contain the root "dec":
* Decade: a period of ten years.
* Decimal: a number system based on ten.
* December: the tenth month of the Roman calendar (though it is now the twelfth month).
* Deciduous: falling off at a particular season, such as leaves from trees. (The word "deciduous" comes from the Latin word "decidere," which means "to fall down.")
Let me know if you'd like to explore other Latin roots!